[ntp:questions] What is the NTP recovery time from 16s step in GPSserver?

David Woolley david at ex.djwhome.demon.invalid
Thu Nov 1 13:36:07 UTC 2012

David Taylor wrote:
> On 01/11/2012 08:40, David Woolley wrote:
>> David Taylor wrote:
>>> On a recent restart from cold, the server here took about 15 minutes
>>> to get to within 250 microseconds, and about an hour to be within 10
>>> microseconds.  Ultimately it is within about 3 microseconds.
>> 3 microseconds of what?  How are you measuring the difference between
>> software clock time and UTC, independently of NTP?
> That's the offset as stated by NTP.

That's not the time error.  Under ideal circumstances, it is several 
times higher than the actual error, but with a low value like that, it 
could easily be orders of magnitude worse (e.g. if there were interrupt 
latencies in the 100s of microseconds and up, or, for network time, if 
there were asymmetric delays in the milliseconds).

At 250 microseconds, do they all have the same sign? The claim for 
chrony would be that it gets to the state where the offsets are balanced 
about zero, much faster.

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